1. Field of the Invention
This invention relates to a vehicle body frame structure, and more particularly, to a vehicle body frame structure that provides an improved connection structure between a front body and a side body.
2. Description of the Related Art
In a vehicle body, various components such as an engine, front wheel suspensions, a radiator, and the like are generally mounted to a front body. Thus, the front body has various parts varying in rigidity. A side body, which is disposed on a rear side of the front body, is required to have a function of suppressing the vehicle body from being deformed in a height direction thereof.
The connection between the front body and the side body is sometimes performed by connecting together a hood ridge member (upper frame) of the front body and an outer panel (body pane) of the side body through an outer frame member. The outer frame member is joined to the hood ridge member and the outer panel from outside of the vehicle body. From the viewpoint of the order of connection between the hood ridge member and the side body, the outer frame member is the component that is finally assembled by welding.
The connection between the outer frame member and the hood ridge member is achieved by performing spot welding to the outer frame member, whereas the connection between the outer frame member and the outer panel is achieved by performing arc welding to the outer panel which is made of a thin sheet material.
As understood, the connection to the side body is not a structural connection. This poses a problem that from the viewpoint of durable strength of the vehicle body, the connection becomes one of the most fracturable parts. In this regard, a technical art of a vehicle body frame structure in which a front body and a side body are bolted together through a reinforcing member is disclosed in Japanese Utility Model Registration No. 3089814 (3rd to 5th paragraphs, FIG. 4, etc.).
In the prior art disclosed in Japanese Utility Model Registration No. 3089814, plates each consisting of a metal sheet are joined together by means of bolts to thereby reinforce the connection between the front body and the side body. This makes it possible to increase the rigidity without occurrences of fracture at weld joint portions.
However, such joining method using bolts can merely achieve reinforcement by means of plates or metal sheets which are small in cross-section effect, and hence the connection to the side body cannot still be considered as a structural connection.
The part of connection to the side body still remains one of the most fracturable parts, and entails a problem of providing a poor endurance strength of the vehicle body. In other words, the prior art disclosed in Japanese Utility Model Registration No. 3089814 does not pay a particular attention to the necessity to achieve a structural connection.
The variety is demanded for recent sedan vehicles, such that vehicles be more sporty and improved in steering performance, and the like. To this end, it is especially required to increase the rigidity of the front body. In this respect, a technical art for a vehicle body frame structure which connects a front body and a side body together with use of a reinforcement is proposed in Japanese Utility Model Registration No. 3070857 (6th to 9th paragraphs, FIG. 2, etc.).
The prior art disclosed in Japanese Utility Model Registration No. 3070857 comprises a diagonal member serving as a reinforcement that is disposed between the front body and the side body.
In order to connect the front body and the side body so as to improve the rigidity of vehicle body, not only the connection to the front body but also the connection to the side body is required to provide a structural connection.
The prior art disclosed in Japanese Utility Model Registration No. 3070857 achieves the connection to the side body by utilizing the reinforcement simply connected to a door hinge. This cannot be considered as a structural connection, and still entails a problem of a poor rigidity of the vehicle body.
In this prior art, the connection part to the front body is arranged to project in the vehicle width direction. With this arrangement, when a force is generated in the front body, more specifically, when input exerting in the height direction of the vehicle body is caused by vibration of a strut tower serving as a suspension tower, for instance, such force cannot reliably and adequately be introduced, resulting in a problem of fear that it is difficult to cope with torsion or bending. That is, this prior art does not pay a special attention to the necessity of increasing the rigidity resisting the input to the strut tower. This causes a problem that it is difficult to cope with the variety of vehicles.